The disclosed embodiments relate to a medical device. Specifically, the disclosed embodiments relate to a balloon catheter to be inserted into a stenosis formed in a blood vessel in order to enlarge the stenosis and restore blood flow.
Conventionally, balloon catheters are widely used as therapeutic catheters for enlarging stenoses formed in blood vessels by inserting the balloon catheter into the stenosis. A balloon catheter mainly includes a balloon acting as an inflating body, an outer shaft welded to the proximal end of the balloon, and an inner shaft inserted into the balloon and the outer shaft. The inner shaft is used for inserting a guide wire. An inflation lumen provided between the outer shaft and the inner shaft is used for passing a liquid (e.g., a contrast medium and a physiological saline) for inflating the balloon.
The distal end of the inner shaft has a distal-end tip made of a soft resin. Thus, even if an operator presses the balloon catheter in a distal direction so as to hit a blood vessel wall with the distal end of the balloon catheter, the balloon catheter hardly damages the blood vessel wall.
However, when the balloon catheter having a soft distal-end tip is inserted into a stenosis, the soft distal-end tip may become caught in the stenosis. If the balloon catheter is forcibly rotated or pulled by an operator while the distal-end tip is caught in the stenosis, the distal-end tip cannot be removed from the stenosis and may break apart from the inner shaft. As a solution to this problem, U.S. Pat. No. 6,918,920 describes a balloon catheter having a connecting tube that covers the distal end of the inner shaft and the rear end of the distal-end tip from the outside.
In the balloon catheter of U.S. Pat. No. 6,918,920, however, when a distal-end tip having a short length is used, a welding area between the outer surface of the distal-end tip and the inner surface of the connecting tube is small. Unfortunately, this reduces the welding strength between the distal-end tip, and the connecting tube and thus the distal-end tip caught in the stenosis may still break apart from the distal end of the inner shaft when the balloon catheter is forcibly rotated or pulled by an operator.